The present invention relates to a single-phase submergible motor for use in a well of water under submerged condition.
FIGS. 1 and 2 of the accompanying drawings illustrate a conventional single-phase submergible motor. The submergible motor comprises a stator 1 composed of a stator core 2 and a stator winding 3 wound around the stator core 2, and a frame 4 molded of a resin material such as polyester or vinyl ester and encasing the stator 1. The frame 4 has a bottomed hole 4a defined in one side thereof, and another bottomed hole 4b defined in an opposite side thereof in diametrically opposite relation to the recess or bottomed hole 4a. A thin cylindrical sleeve 5 of stainless steel is placed in and held against the inner peripheral surfaces of the stator core 2 and the frame 4. A bracket 6 of molded resin is fastened to one end of the frame 4 and has a bottomed hole 6a opening toward frame 4 in coaxial relation to the hole 4a and another hole 6b opening toward the frame 4 in coaxial relation to the hole 4b. The bracket 6 also has a through hole 6c communicating between the hole 6a and an outer end surface thereof.
The submergible motor also includes a rotor core 7 coacting with the stator motor 2. A rotor shaft 8 is fitted in an inner peripheral surface of the rotor core 7 and has one end portion rotatably supported by a sleeve bearing 9 in the bracket 6, the rotor shaft 8 having an end projecting from the outer end surface of the bracket 6. A water deflector 10 is fitted over the end of the rotor shaft 8 projecting from the bracket 6 and has one end surface held in slidable contact with an outer end surface of the bracket 6. A water seal 11 composed of an oil seal is fitted in an inner peripheral surface of the bracket 6. A male connector 12 for connection to the stator is encased in the bottomed hole 4a. Lead wires 13 have opposite ends connected respectively to the male connector 12 and the stator winding 3. A female connector 14 for connection to a power supply is fitted in the bottomed holes 4a, 6a and connected to contact pins 12a of the male connector 12. A power cable 15 has one end connected to the female connector 14 and extends through the hole 6c, the power cable 15 having an opposite end coupled to a power supply (not shown). A starter switch unit 16 is disposed resiliently in a recess 6d defined in the bracket 6. A male connector 17 for connection to the starter switch unit 16 is encased in the bottomed hole 4b, and a female connector 18 for the starter switch unit 16 is fitted in the bottomed holes 4b, 6b. A male connector 19 for the starter switch unit 16 is encased in the bottomed hole 6b. The male connector 18 for the starter switch unit 16 and the male connector 12 for the stator are interconnected by lead wires 20 encased in the frame 4. The starter switch unit 16 and the male connector 19 are connected to each other. The male connectors 17, 19 have contact pins 17a, 19a joined to the female connector 18. Four threaded members 21 (FIG. 2) are embedded in the frame 4 and have openings that open toward the bracket 6. Threaded fasteners (not shown) are threadedly inserted in the threaded members 21 to couple the frame 4 and the bracket 6 together.
When lightning strikes the submergible motor thus constructed, a lightning surge finds its way from the power cable 15 to the power supply connector 14 to the stator connector 12 to the lead wires 13 to the stator winding 3, with the result that the power cable 15 and the motor as a whole are subjected to severe damage.